Two Humpback Whales Head Up California River

SACRAMENTO, California – A pair of wayward humpback whales continued their improbable odyssey Tuesday, swimming to the outskirts of the state capital.

The whales eluded marine biologists and law enforcement patrols who had searched for them throughout the day but were spotted Tuesday evening by a helicopter pilot for KCRA-TV in the deep water shipping channel south of Sacramento.

Footage showed the whales — believed to be a mother and her calf — plying the canal about two miles south of the Port of Sacramento .

• Click here to visit FOXNews.com's Natural Science Center.

They were headed upriver toward the turning basin used for deep-water ships, a journey of more than 50 miles from the point where the Sacramento and San Joaquin rivers merge at Suisun Bay .

He said a team of experts was planning to arrive in Sacramento on Wednesday to assess the health of the whales and how they can be lured back toward the ocean.

The whales were spotted in the lower Sacramento River over the weekend and caused a sensation on Monday when they surfaced repeatedly near the delta towns of Isleton and Rio Vista.

Marine experts had expected to spend Tuesday evaluating the whales after the larger one appeared to be entangled in fishing gear. But they searched in vain until the television helicopter spotted them.

The team will determine if the object needs to be removed.

"If there is fishing line on, like there appears to be from the helicopters, it will be a question of how badly it is entangled and can it swim and survive, or not," he said.

While it's unusual for whales to reach so far into the delta, it is not the first time. In 1985, a humpback nicknamed Humphrey was escorted back to sea after swimming in the delta for nearly a month. He returned to San Francisco Bay five years later.